Adjust roller bridge height on Mosrite Mark I?

[rballister]

My 80's Mosrite Mark I hasn't been played for about a year. Tuned it up and noticed the first string is fretting out. I've been staring at the roller bridge for the last 10 minutes and I'm not sure which screw to turn! (more used to strat and tele adjustments). The two choices seem to be a bolt with a round top near the first string that looks like it takes some sort of socket wrench. If it does take a socket wrench does anyone know what size? The other choice is one of three screws (I presume the one near the first string). I'm guessing turning these screws counterclockwise will slightly raise the height of the first string. (as the other strings aren't fretting out I'm guessing I can make this small adjustment without messing with the truss rod) While I'm asking (might as well get all the questions out there) I'm presuming the six screws for intonation work the same as on other guitars--turning them clockwise lengthens the string (if sharp). By the way is there any sort of Mosrite PDF adjustments manual out there? Thanks in advance for any help.

[juan_10]

I'll try Height adjustment .. the two slot head screws either side of the bridge .. there is no individual height adjustment for the seperate strings .. just the whole assembly.

Intonation .. the cross headed screws under each roller stud are capped with a locking nut at the other end ( acorn nuts ), you will need to loosen off the locking nut to do the adjustment and then tighten it up afterwards (I use a pair of needle nose pliers , but this is not good..it will end up rounding off the nuts .. better to get a small spanner )



Hope I helped a bit

[rballister]

Thank you! But there is one difference between my roller bridge and yours. Where you have two slot head screws to make the height adjustments I have two (well I'm not sure what they are) acorn screws(?). My guess is that its a screw with an acorn like head. A long time ago I e-mailed Andy Moseley (at least I think it was Andy!) about the instrument who thought some of the parts on the instrument might be Mosrtie 1990 parts, but he couldn't be sure without actually handling the instrument. If the bridge height adjustment is some sort of acorn topped screw I would have to use needle nose pliers or a very tiny wrench (not sure a wrench would fit). As I would have to twist them sideways I would not have the advantage of a vertical screw driver which would be very easy. If I don't use the needle nose pliers (scary---one slip and there goes the finish) the only other thing I can think of is some sort of tiny vertical socket wrench (which I've never seen). What would you use?
(By the way after staring at the three small screws I'm pretty sure they hold down a narrow plate which keeps things tight in the bridge.)

[juan_10]

Thanks for the photo it makes it easier ... I'd have a look for a tiny spanner set .. bike shop style .. for adjusting the 'acorn' headed screws , you are right about the needle nosed pliers .. they can be deadly to the finish if they slip ! It looks like the plate with the three screws does the lock down job that the acorn nuts do on the photo I posted.
Now there is a piccy of your bridge up on the board someone with more Mosrite experince will surely chime in and help us out, because , to be frank , I've not seen one like that before on a Mosrite .
Just thinking aloud here, but if you haven't touched it for a year and now you find the top E fretting out , maybe the neck has 'moved' during that time due to humidity changes etc (I know it gets quite hot and humid in New York ). So maybe a good thing would be to give the neck a quick once over to be sure it's not just a simple truss rod adjust . Don't panic

[rballister]

Thanks for the reply juan-10. I'm hoping someone else will chime in too (I PMed one of the builders). Maybe there is some sort of special tool to use on those acorn (?) screws that can be used vertically.

[Mr. Bill]

The tool you are thinking of is called a nutdriver, a screwdriver for nuts.

I don't know for sure, but I'd guess that the acorn nuts are there to lock the bridge in position, and there are two normal hex nuts under the bridge that set the height.

[rballister]

Thanks for the reply Mr. Bill. If there are a hex nuts under the acorn nut this is one convoluted bridge design!

[Mr. Bill]

What I am thinking is that there will be hex nuts under the bridge baseplate that control the height of the bridge and the acorn nuts are there to lock down the adjustment and to keep the bridge from moving.

[rballister]

If they are under the bridge plate I guess I would have to completely remove the bridge to get to them, make an adjustment, reassemble the bridge and hope I got it right.

[Mr. Bill]

Can you post a side view photo of the bridge?